Presumably. I know it was announced that she's mortal. But unless they show her death scene, hopefully in battle, perhaps killed by Trixie, Sombra,Chrysalis or Flam, I reserve the right to be skeptical and will expect her to live on forever. Especially if Hasbro forgets about the promise and he last scene of the final episode is showing Twilight (maybe in the company of the royal sisters) standing on the lest say balcony or next to a set of graves a few hundreds years later and concluding with something like. "I knew how friendship used to feel" or something.

Yes the unfortunate curse of being a princess of these lands. Absolute immortality, meaning they are forced to watch their loved ones slowly wither and die, hopefully of old age, over and over again soon making them long for the kind hand of death, whom shall never come to alleviate the heaviest of burdens.